1. Field of the Invention
The present invention relates to a light transmission and reception module, and more particularly to a light transmission and reception module for transmitting and receiving an optical signal by way of an optical waveguide formed on a macromolecular optical waveguide film. The invention also relates to a sub-mount used in this light transmission and reception module, and a method of manufacturing the same sub-mount.
2. Description of the Related Art
Hitherto, various methods of manufacturing a macromolecular optical waveguide have been proposed, including (1) a method of impregnating a film with a monomer, exposing the core selectively to change the refractive index thereof, and effecting attachment of the film (selective polymerization method), (2) a method of providing a core layer and a clad layer by coating, and forming the clad by reactive ion etching (RIE method), (3) a method of using photolithography, in which exposure and development are effected by using an infrared curable resin obtained by adding a photosensitive material to a macromolecular material (direct exposure method), (4) a method of injection molding, and (5) a method of providing a core layer and a clad layer by coating, and exposing the core to change the refractive index of the core (photo bleaching method).
However, in the selective polymerization method (1), there are problems in adhesion of the film. In the methods (2) and (3), the cost is high because of photolithography. The method of (4) has problems in precision of the obtained core diameter. In the method of (5), a sufficient difference in refractive index is not obtained between the core layer and clad layer.
Excellent and practical methods from the viewpoint of performance are the methods (2) and (3) only, but they are costly. Further, any one of the methods (1) to (5) is not applicable to formation of macromolecular optical waveguide in a wide and flexible plastic substrate.
By contrast, the present inventors have previously proposed a method of manufacturing a macromolecular optical waveguide by using a mold (specifically, by what is called “micro-mold method”), which method is completely different from the conventional methods of manufacturing a macromolecular optical waveguide (see Japanese Patent Application Laid-open Nos. 2004-29507, 2004-86144, and 2004-109927).
According to this method, mass production of macromolecular optical waveguides is possible very easily and at low cost. In spite of the easy method, a macromolecular optical waveguide with a small waveguide loss can be formed, and any pattern can be formed easily as far as a mold can be made. It is further possible to form an optical waveguide on a hitherto difficult flexible plastic substrate.
Recently, in the IC technology or LSI technology, in order to enhance the operating speed and degree of integration, it has been proposed to form optical wiring between devices, between boards in device, or in chips, instead of placing electrical wiring at high density. Various devices are proposed for optical winding using surface emission type laser and surface photo detectors such as photo diodes advantageous for saving energy and forming surface arrays.
As such device, Japanese Patent Application Laid-open No. 2000-39530 discloses an optical device comprising a core, a macromolecular optical waveguide having a clad for enveloping the core, a photo transmitter and a photo detector disposed in the laminating direction of core and clad, an incident surface mirror for receiving the light from the light emitting element and making the light be incident on the core, and an exit surface mirror for emitting the light from the core to the photo detector, in which the clad layer is formed in a concave shape at a position corresponding to the optical path reaching from the photo emitter to the incident surface mirror and from the exit surface mirror to the photo detector, and the light from the light emitting element and the light from the exit surface mirror are converged.
Japanese Patent Application Laid-open No. 2000-39531 discloses an optical device for making the light from a light emitting element be incident on the core end surface of a macromolecular optical waveguide having a core and a clad for enveloping the core, in which the light incident end surface of the core is formed in a convex shape toward the light emitting element, and the light from the light emitting element is converged to suppress the waveguide loss.
Japanese Patent Application Laid-open No. 2000-235127 discloses a photoelectronic integrated circuit in which a macromolecular optical waveguide circuit is directly assembled on an integrated photoelectric fusion circuit board of electronic element and optical element.
In any one of these methods of optical wiring proposed so far, the optical waveguide is fixed on the substrate together with the light emitting and detecting elements and the mirrors, and as compared with electrical wiring, the degree of freedom of wiring is smaller, and it can be hardly applied in narrow and plaited wiring of cellphones, slim personal computers, and mobile appliances.
On the other hand, a flat optical fiber tape bundling several strands of resin-coated optical fibers is used in optical wiring, but the optical fiber is made of quartz glass tube and is not resistant to bending and folding, and the degree of freedom of wiring is also small.
In addition to these problems, in the methods of manufacturing a macromolecular optical waveguide proposed so far, it is required to bury a mirror in order to form a 90-degree folding mirror, or positioning at high precision is required in the case of adhering a waveguide and light emitting and detecting elements, whereby the mounting cost is high.
By contrast, the present inventors have previously invented a macromolecular optical waveguide module with light emitting and detecting elements having a macromolecular optical waveguide film including the optical waveguide duplicated by a mold, and already filed an application therefor (Japanese Patent Application Laid-open No. 2004-139041). In this macromolecular optical waveguide film, an optical path conversion mirror surface and abutting surface are provided on a same end. An abutting surface at which an abutting surface of a film is abutted is formed in a submount holding the light receiving-detecting element. In this module, when mounting, the abutting surface of the film is abutted to the abutting surface formed on the sub-mount, and the light emitting and detecting elements and optical path conversion surface can be positioned precisely and easily.
Japanese Patent Application Laid-open No. 2000-114655 discloses a semiconductor laser device for converting the optical path of laser beam by a mirror surface by forming the mirror surface on the sub-mount of semiconductor laser.
For the precise processing of such sub-mount, however, each submount must be processed by fine processing technology such as reactive ion etching (RIE), and the manufacturing cost of the sub-mount becomes very high.